Many modern devices include some form of display, such as a flatscreen or projector, for displaying content. To ensure that displayed content can be clearly seen by a user in varying lighting conditions, many devices include an ambient light sensor to detect the ambient brightness and adapt the display brightness accordingly. In bright conditions, the display brightness is increased to ensure that high contrast is maintained, whereas in dim conditions the display brightness is decreased to conserve power. However, even in similar viewing conditions, the user experience can vary from one person to the next. For example, one person may be able to easily read displayed text under certain conditions, whereas a user with poor eyesight may struggle to read the same displayed text under the same conditions. Such individual factors are not taken into account by conventional systems.